linq - Linq 分配给 List<> 列表绑定

Question

我在运行时收到此错误：

异常详细信息：System.InvalidOperationException：未处理的绑定类型：ListBinding

• Choice_A、_b、_C 是字符串
• “选择”是列表

---

  var qs = (from questions in dc.Survey_Questions
                      where questions.Survey_ID == surveyid                     
                      select new SQuestions
                      {
                          QuestionID = questions.Question_ID,                          
                          Description = questions.Description,
                          Choice_A = questions.Choice_A,  
                          Choice_B = questions.Choice_B,  
                          Choice_C = questions.Choice_C,
                         **Choices =  {questions.Choice_A, questions.Choice_B,
          questions.Choice_C}**
   }).ToList();

基本上我想知道我如何分配给Choice_A、Choice_B、Choice_C 的List Choices 值。提前致谢。

Answer 1

你可以试试这个。如果你已经有以下两个类

public class Question
{
    public int Question_ID { get; set; }
    public int Survey_ID { get; set; }

    public String Description { get; set; }
    public String Choice_A { get; set; }
    public String Choice_B { get; set; }
    public String Choice_C { get; set; }
}

public class SQuestions
{
    public int QuestionID { get; set; }
    public String Description { get; set; }
    public String Choice_A { get; set; }
    public String Choice_B { get; set; }
    public String Choice_C { get; set; }

    public List<String> Choices { get; set; }
}

然后 LINQ 查询将是

var qs = (from question in dc.Survey_Questions
where question.Survey_ID == surveyid
select new SQuestions
{
   QuestionID = question.Question_ID,
   Description = question.Description,
   Choice_A = question.Choice_A,
   Choice_B = question.Choice_B,
   Choice_C = question.Choice_C,
   Choices = new List<string>(new String[] { question.Choice_A,question.Choice_B, question.Choice_C })
}).ToList();

Answer 2

LINQ to Entities 不支持此绑定语法。不过，您应该能够做到这一点：

qs = (from questions in dc.Survey_Questions
                  where questions.Survey_ID == surveyid                     
                  select new SQuestions
                  {
                      QuestionID = questions.Question_ID,                          
                      Description = questions.Description,
                      Choice_A = questions.Choice_A,  
                      Choice_B = questions.Choice_B,  
                      Choice_C = questions.Choice_C,
                     Choices = new List<string> {questions.Choice_A, questions.Choice_B,
      questions.Choice_C}
}).ToList();